U.S. patent application number 12/416034 was filed with the patent office on 2010-09-30 for exhaust plenum for a turbine engine.
This patent application is currently assigned to General Electric Company. Invention is credited to Laxmikant Merchant, Prabhakaran Saraswathi Rajesh.
Application Number | 20100247304 12/416034 |
Document ID | / |
Family ID | 42309554 |
Filed Date | 2010-09-30 |
United States Patent
Application |
20100247304 |
Kind Code |
A1 |
Merchant; Laxmikant ; et
al. |
September 30, 2010 |
EXHAUST PLENUM FOR A TURBINE ENGINE
Abstract
An exhaust system for gas turbine engine is provided that
reduces turbulence and backflow within the exhaust system and,
thus, increases the efficiency of the turbine engine. In various
embodiments, the system includes an exhaust plenum that provides a
gradual expansion of the exhaust gases. The exhaust plenum may also
include one or more flow splitters that further reduce turbulence
in the plenum and provide a more uniform gas flow in the plenum and
other downstream exhaust components.
Inventors: |
Merchant; Laxmikant;
(Karnataka, IN) ; Rajesh; Prabhakaran Saraswathi;
(Trivandrum, IN) |
Correspondence
Address: |
GE Energy-Global Patent Operation;Fletcher Yoder PC
P.O. Box 692289
Houston
TX
77269-2289
US
|
Assignee: |
General Electric Company
Schenectady
NY
|
Family ID: |
42309554 |
Appl. No.: |
12/416034 |
Filed: |
March 31, 2009 |
Current U.S.
Class: |
415/207 ;
415/226 |
Current CPC
Class: |
Y02T 50/671 20130101;
F05D 2260/97 20130101; B64D 33/04 20130101; F02K 1/002 20130101;
F05D 2210/42 20130101; B64D 33/06 20130101; F01D 25/30 20130101;
Y02T 50/60 20130101 |
Class at
Publication: |
415/207 ;
415/226 |
International
Class: |
F01D 25/24 20060101
F01D025/24; F01D 1/06 20060101 F01D001/06 |
Claims
1. A system, comprising: a turbine engine comprising a radial
diffuser disposed about a first axis downstream in an exhaust flow
path from a turbine section; and an exhaust plenum, comprising: an
inlet, wherein the radial diffuser is disposed through the inlet
into the exhaust plenum, and the exhaust plenum extends along a
second axis crosswise relative to the first axis of the turbine
engine; a flow splitter extending completely across the exhaust
plenum along the first axis, wherein the flow splitter extends in a
first direction radially outward from the radial diffuser relative
to the first axis, and the flow splitter bends from the first
direction to a second direction downstream along the second axis;
and a set of first and second aerodynamic surfaces facing one
another about the radial diffuser, wherein the first and second
aerodynamic surfaces are axially offset from one another by an
axial offset along the first axis, and the first and second
aerodynamic surfaces gradually expand the axial offset with
increasing radial distance away from the first axis.
2. The system of claim 1, wherein the radial diffuser comprises a
plurality of circular vanes disposed about the first axis, and the
flow splitter extends in the first direction radially outward from
the vanes.
3. The system of claim 1, wherein the flow splitter bends at least
approximately 90 degrees from the first direction to the second
direction.
4. The system of claim 1, wherein the flow splitter extends in the
first direction at an angle of approximately 90 degrees relative to
the second axis.
5. The system of claim 1, wherein the flow splitter extends
downstream along the second axis to an axial offset away from the
radial diffuser.
6. The system of claim 1, wherein the flow splitter extends from
the first direction to the second direction with a length of at
least greater than a radius of the radial diffuser.
7. The system of claim 1, comprising another flow splitter
extending completely across the exhaust plenum along the first
axis, wherein the other flow splitter extends in a third direction
radially outward from the radial diffuser relative to the first
axis, the other flow splitter bends from the third direction to a
fourth direction downstream along the second axis
8. The system of claim 1, wherein the first and second aerodynamic
surfaces comprise conical surfaces diverging away from one another
in an outward radial direction away from the first axis.
9. The system of claim 1, wherein the first and second aerodynamic
surfaces comprise diverging surfaces that diverge away from one
another in an outward radial direction away from the first axis at
a rate of less than about 115 percent of a change in axial offset
versus a change in radial distance.
10. A system, comprising: a turbine exhaust plenum, comprising: an
inlet coupled to a diffuser region configured to receive a radial
diffuser of a turbine engine along a first axis, wherein the
turbine exhaust plenum extends along a second axis crosswise
relative to the first axis; and a flow splitter extending
completely across the turbine exhaust plenum along the first axis
adjacent the diffuser region, wherein the flow splitter extends
from an upstream end to a downstream end with a length of at least
greater than a radius of the radial diffuser, and the flow splitter
bends from the upstream end to the downstream end over an angle of
at least approximately 90 degrees.
11. The system of claim 10, wherein the flow splitter is configured
to split and route exhaust flow to provide a substantially uniform
flow distribution.
12. The system of claim 10, wherein the diffuser region is
positioned in the turbine exhaust plenum at an off-center position
relative to the first axis, and wherein the diffuser region is
closer to a first side and farther from a second side opposite from
the first side about the first axis, and the flow splitter is
disposed on the second side.
13. The system of claim 10, wherein the flow splitter comprises
first and second flow splitters disposed on opposite first and
second sides of the diffuser region about the first axis, each of
the first and second flow splitters has the length of at least
greater than the radius of the radial diffuser, and each of the
first and second flow splitters bends from the upstream end to the
downstream end over the angle of at least approximately 90
degrees.
14. The system of claim 10, wherein the diffuser region is centered
within the turbine exhaust plenum relative to a width of the
turbine exhaust plenum along the first axis, and the diffuser
region is centered within the turbine exhaust plenum relative to a
height of the turbine exhaust plenum along a third axis crosswise
to both the first and second axes.
15. The system of claim 10, comprising a second flow splitter
extending completely across the turbine exhaust plenum along the
first axis adjacent the diffuser region, wherein the second flow
splitter extends from an second upstream end to a second downstream
end, and the first downstream end and the second downstream end lie
in a plane orthogonal to the second axis.
16. The system of claim 10, comprising aerodynamic surfaces
positioned about the first axis and surrounding the inlet, wherein
the aerodynamic surfaces provide an initial plenum width at the
inlet and gradually slope outward to a full plenum width at a
location radially away from the inlet relative to the first
axis.
17. A system, comprising: a turbine exhaust plenum, comprising: an
inlet coupled to a diffuser region configured to receive a radial
diffuser of a turbine engine along a first axis, wherein the
turbine exhaust plenum extends along a second axis crosswise
relative to the first axis; and a set of first and second
aerodynamic surfaces disposed opposite from one another relative to
the diffuser region, wherein the first and second aerodynamic
surfaces diverge away from one another in an outward radial
direction away from the first axis.
18. The system of claim 17, wherein the first and second
aerodynamic surfaces comprise conical surfaces diverging away from
one another in the outward radial direction away from the first
axis.
19. The system of claim 18, wherein the conical surfaces are
axially offset from one another by an axial offset along the first
axis.
20. The system of claim 19, wherein the conical surfaces diverge
away from one another in the outward radial direction away from the
first axis at a rate of less than about 115 percent of a change in
the axial offset versus a change in radial distance.
Description
BACKGROUND OF THE INVENTION
[0001] The subject matter disclosed herein relates to gas turbine
engines, and more specifically, to exhaust systems for gas turbine
engines.
[0002] In general, gas turbine engines combust a mixture of
compressed air and fuel to produce hot combustion gases. The
combustion gases may flow through one or more stages of turbine
blades to generate power for a load and/or a compressor. The gas
turbine engine may exhaust the combustion gases into an exhaust
system, which safely routes the combustion gases to the atmosphere.
Unfortunately, the exhaust system generally creates backpressure to
the gas turbine engine, which reduces performance of the gas
turbine engine. Furthermore, efforts to make this exhaust system
more compact have resulted in more complicated and expensive
systems with a significant level of backpressure to the gas turbine
engine.
BRIEF DESCRIPTION OF THE INVENTION
[0003] Certain embodiments commensurate in scope with the
originally claimed invention are summarized below. These
embodiments are not intended to limit the scope of the claimed
invention, but rather these embodiments are intended only to
provide a brief summary of possible forms of the invention. Indeed,
the invention may encompass a variety of forms that may be similar
to or different from the embodiments set forth below.
[0004] In one embodiment, a system includes a turbine engine
comprising a radial diffuser disposed about a first axis downstream
in an exhaust flow path from a turbine section and an exhaust
plenum. The exhaust plenum may include an inlet, wherein the radial
diffuser is disposed through the inlet into the exhaust plenum, and
the exhaust plenum extends along a second axis crosswise relative
to the first axis of the turbine engine. The exhaust plenum also
includes a flow splitter extending completely across the exhaust
plenum along the first axis, wherein the flow splitter extends in a
first direction radially outward from the radial diffuser relative
to the first axis, and the flow splitter bends from the first
direction to a second direction downstream along the second axis.
The exhaust plenum also includes a set of first and second
aerodynamic surfaces facing one another about the radial diffuser,
wherein the first and second aerodynamic surfaces are axially
offset from one another by an axial offset along the first axis,
and the first and second aerodynamic surfaces gradually expand the
axial offset with increasing radial distance away from the first
axis.
[0005] In another embodiment, a system includes a turbine exhaust
plenum with an inlet coupled to a diffuser region configured to
receive a radial diffuser of a turbine engine along a first axis,
wherein the turbine exhaust plenum extends along a second axis
crosswise relative to the first axis. The turbine exhaust plenum
also includes a flow splitter extending completely across the
turbine exhaust plenum along the first axis adjacent the diffuser
region, wherein the flow splitter extends from an upstream end to a
downstream end with a length of at least greater than a radius of
the radial diffuser, and the flow splitter bends from the upstream
end to the downstream end over an angle of at least approximately
90 degrees.
[0006] In another embodiment, a system includes a turbine exhaust
plenum with an inlet coupled to a diffuser region configured to
receive a radial diffuser of a turbine engine along a first axis,
wherein the turbine exhaust plenum extends along a second axis
crosswise relative to the first axis. The exhaust plenum also
includes a set of first and second aerodynamic surfaces disposed
opposite from one another relative to the diffuser region, wherein
the first and second aerodynamic surfaces diverge away from one
another in an outward radial direction away from the first
axis.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] These and other features, aspects, and advantages of the
present invention will become better understood when the following
detailed description is read with reference to the accompanying
drawings in which like characters represent like parts throughout
the drawings, wherein:
[0008] FIG. 1 is a schematic flow diagram of an embodiment of a gas
turbine engine with an improved exhaust plenum;
[0009] FIG. 2 is a sectional view of the gas turbine engine as
shown in FIG. 1, illustrating an embodiment of the improved exhaust
plenum;
[0010] FIG. 3 is a cut-away perspective view of an embodiment of
the exhaust plenum, as shown in FIG. 1, with conical surfaces and a
flow guide;
[0011] FIG. 4 is a cut-away top view of the exhaust plenum of FIG.
3;
[0012] FIG. 5 is a cut-away side view of the exhaust plenum of FIG.
3;
[0013] FIG. 6 is a cut-away side view of the exhaust plenum of FIG.
3, illustrating air flow in the plenum, in accordance with
embodiments;
[0014] FIG. 7 is a cut-away side view of an embodiment of the
exhaust plenum, as shown in FIG. 1, with two flow splitters;
and
[0015] FIG. 8 is a cut-away side view of an embodiment of the
exhaust plenum, as shown in FIG. 1, with a symmetrical
configuration having four flow splitters and a rounded back
plate.
DETAILED DESCRIPTION OF THE INVENTION
[0016] One or more specific embodiments of the present invention
will be described below. In an effort to provide a concise
description of these embodiments, all features of an actual
implementation may not be described in the specification. It should
be appreciated that in the development of any such actual
implementation, as in any engineering or design project, numerous
implementation-specific decisions must be made to achieve the
developers' specific goals, such as compliance with system-related
and business-related constraints, which may vary from one
implementation to another. Moreover, it should be appreciated that
such a development effort might be complex and time consuming, but
would nevertheless be a routine undertaking of design, fabrication,
and manufacture for those of ordinary skill having the benefit of
this disclosure.
[0017] When introducing elements of various embodiments of the
present invention, the articles "a," "an," "the," and "said" are
intended to mean that there are one or more of the elements. The
terms "comprising," "including," and "having" are intended to be
inclusive and mean that there may be additional elements other than
the listed elements.
[0018] The present disclosure is directed to a gas turbine engine
that includes an exhaust system that provides improved pressure
recovery and reduced backpressure and, therefore, increases the
efficiency of the turbine engine. In a gas turbine engine with a
hot-end drive, a rotating shaft coupled to the turbine passes
through the turbine at the exhaust end and is coupled to a
generator or other load. Therefore, as the exhaust gases exit the
turbine, the exhaust gases are guided through an exhaust duct that
that extends outward away from the axis of the shaft to avoid the
load (e.g., in a crosswise or radial direction). This change in the
direction of exhaust flow (e.g., axial to radial) may tend to cause
turbulence (e.g. swirling motion of the gases), which in turn
causes significant backpressure. Additionally, as the combustion
gases exit the turbine, the gases typically enter a high volume
exhaust plenum that causes a sudden expansion of the gases, which
also causes increased turbulence inside the plenum and produces
non-uniform gas flow in the plenum and other downstream
components.
[0019] Embodiments of the present invention provide an exhaust
plenum that provides a gradual expansion of the exhaust gases
within the plenum and thereby reduces the turbulence within the
plenum. Additionally, embodiments may also include one or more flow
splitters that further reduce turbulence in the plenum and produce
a more uniform gas flow in the plenum and other downstream exhaust
components. Further embodiments include a symmetrical exhaust
plenum that reduces turbulence even further by producing an even
more uniform gas flow within the plenum. The overall result is
reduced backpressure and increased flow uniformity in the exhaust
system. Furthermore, the exhaust plenum described herein is more
compact than typical exhaust plenums, and uses less material, which
reduces costs and space consumption at a facility.
[0020] FIG. 1 is a schematic flow diagram illustrating an
embodiment of a gas turbine engine with an improved exhaust system.
In certain embodiments, the system 10 may include an aircraft, a
watercraft, a locomotive, a power generation system, or
combinations thereof. The illustrated gas turbine engine 12
includes an air intake section 16, a compressor 18, a combustor
section 20, a turbine 22, and an exhaust section 24. The turbine 22
is drivingly coupled to the compressor 18 via a shaft 26 oriented
along a longitudinal axis 27 of the turbine engine 12. The shaft is
drivingly coupled to a load 14, which may be positioned at the
exhaust end of the turbine engine 12.
[0021] As indicated by the arrows, air may enter the gas turbine
engine 12 through the intake section 16 and flow into the
compressor 18, which compresses the air prior to entry into the
combustor section 20. The illustrated combustor section 20 includes
a combustor housing 28 disposed concentrically or annularly about
the shaft 26 axially between the compressor 18 and the turbine 22.
The compressed air from the compressor 18 enters combustors 30
where the compressed air may mix and combust with fuel within the
combustors 30 to drive the turbine 22.
[0022] From the combustor section 20, the hot combustion gases flow
through the turbine 22, driving the compressor 18 and the load 14
via the shaft 26. For example, the combustion gases may apply
motive forces to turbine rotor blades within the turbine 22 to
rotate the shaft 26. After flowing through the turbine 22, the hot
combustion gases may exit the gas turbine engine 12 through the
exhaust section 24. As the combustion gases pass from the exhaust
section 24 to the exhaust plenum 32, the plenum 32 guides the
combustion gases at an angle away from a longitudinal axis 27 of
turbine engine 12 (e.g., approximately 90 degrees). In other words,
the exhaust plenum 32 is oriented crosswise or transverse to the
longitudinal axis 27, e.g., a radial direction. For example, the
illustrated turbine engine 12 includes a radial duct or plenum 32
to route the combustion gases through a 90 degree turn relative to
the longitudinal axis 27. The change in direction (e.g., 90 degree
turn) tends to induce turbulence and increase the backpressure on
the turbine, thus decreasing the efficiency of the turbine. As will
be explained further below, the plenum 32 includes various
improvements that reduce the turbulence and backpressure. For
example, the plenum 32 may include one or more gradual expansion
surfaces (e.g., opposite conical surfaces), flow splitters, and
symmetrical arrangements to increase uniformity in the gas flow.
After leaving the plenum 32, the combustion gases may pass through
one or more silencers 34 that attenuate noise emitted by the
turbine engine 12. From the silencers 34, the combustion gases then
flow through an exhaust stack 36 to the outside environment.
[0023] FIG. 2 is a cross-sectional side view of the gas turbine
engine 12 of FIG. 1, illustrating an embodiment of the improved
exhaust plenum 32 of FIG. 1. To aid in the present description,
orthogonal axes are defined which are consistent through the
present specification. In some embodiments, these axes may be
described as crosswise or transverse to one another, such that the
angles between axes may not be limited to only 90 degrees.
Specifically, the x-axis, indicated by arrow 31, is the central
axis of the turbine engine 12; the y-axis, shown by arrow 33, is
the vertical axis; and the z-axis, which points out of the page in
the present view, points toward the general flow direction of the
plenum 32 (See FIG. 3, arrow 35). As described above with respect
to FIG. 1, air may enter through the air intake section 16 and be
compressed by the compressor 18. The compressed air from the
compressor 18 may then be directed into the combustor section 20
where the compressed air may be mixed with fuel (e.g., liquid
and/or gas fuel). The mixture of compressed air and fuel is
generally burned within the combustor section 20 to generate
high-temperature, high-pressure combustion gases, which may be used
to generate torque within the turbine 22. Specifically, the
combustion gases may apply motive forces to buckets (e.g., turbine
blades) of rotor assemblies 38 to turn wheels 40 and the shaft 26.
As is more clearly shown in FIG. 2, the exhaust section 24 may
include a radial diffuser 42 that guides the combustion gases
annularly about the shaft 26 along the x-axis 31. The volume of the
diffuser 42 gradually increases toward a diffuser output 44,
thereby gradually reducing the pressure and airflow speed within
the diffuser 42.
[0024] At the diffuser output 44, the combustion gases turn at
approximately a 90 degree angle and flow into the plenum 32. To
reduce turbulence in the diffuser 42, the diffuser output 44 may
include several radial guide vanes 46 that guide the combustion
gases through the 90 degree turn into the plenum 32 and improve the
flow uniformity through the diffuser output 44. The diffuser 42 is
disposed through an inlet 47 of the plenum 32, and the diffuser
output 44 is fluidly coupled to the corresponding plenum inlet 47.
As shown in FIG. 2, the initial width 48 of the plenum 32 at the
plenum inlet 47 matches the width of the diffuser output 44.
Therefore, the combustion gases do not experience a sudden
expansion and drop in pressure upon entering the plenum 32, which
is contrastingly different than other turbine exhaust systems.
[0025] After entering the plenum 32, the combustion gases are
guided along aerodynamic surfaces, e.g., opposite sloping surfaces
50, inside the plenum 32. For example, the sloping surfaces 50 may
be described as aerodynamic by virtue of their design with
curvatures to reduce flow resistance, turbulence, and back
pressure. These sloping surfaces 50 enable the combustion gases to
gradually expand within the plenum 32, thus further inhibiting
turbulent flow. In some embodiments, a slope angle 56 may be
approximately 5 to 40 degrees, or 10 to 30 degrees, or 20 degrees.
Additionally, the slope angle 56 may depend on the ratio of the
initial width 48 of the plenum 32 to a full width 52 of the plenum
32 and the amount of space available inside the plenum 32. In some
embodiments, full width 52 of the plenum 32 may be approximately
1.5 to 5 times or 2 to 3 times the initial width 48 of the plenum
32 and the length 54 of the slope may be approximately 20 to 30
inches. More specifically, the initial width 48 of the plenum 32
may be approximately 27 inches, the full width 52 of the plenum 32
may be approximately 70 inches, and the length 54 of the slope may
be approximately 25 inches. In alternate embodiments, the full
plenum width 52 may be approximately the same as the initial plenum
width 48 and the slope angle 56 may be approximately zero degrees.
The height 58 of the plenum 32 may be approximately 5 to 15 times
or 7 to 9 times the initial width 48 of the plenum 32. More
specifically, the height 58 of the plenum may be approximately 205
inches.
[0026] As shown in FIG. 2, the diffuser output 44 is not positioned
centrally within the plenum 32. Therefore, the flow characteristics
will be different near the bottom 62 of the plenum 32 compared to
the top 60 of the plenum 32. In other embodiments, which will be
described further below with reference to FIG. 8, the diffuser
output 44 may be centrally located inside the plenum 32 such that
the flow characteristics are the same at the top and the bottom of
the plenum 32, thereby further increasing the flow uniformity in
the plenum 32 and other exhaust components further downstream.
[0027] FIG. 3 is a cut-away perspective view of an embodiment of
the plenum 32 shown in FIG. 2. As described above in reference to
FIG. 2, the diffuser 42 guides the combustion gases into the plenum
32 through the radial guide vanes 46. As is more clearly shown in
FIG. 3, the radial guide vanes 46 may be circular (e.g., tapered
annular or conical structures) and disposed concentrically about
the x-axis 31. Accordingly, the combustion gases may exit the
diffuser 42 radially outward and away from the axis of the shaft
26, i.e. the x-axis 31, about the circumference of the annular
diffuser output 44. As is also more clearly shown in FIG. 3, the
sloping surfaces 50 may be tapered annular surfaces formed by one
or more cones 78 centered approximately about the diffuser output
44. The sloping surfaces 50 gradually broaden the width of the air
flow path as the combustion gases travel away from the x-axis 31.
In some embodiments, the sloping surfaces 50 may be shaped
differently within different areas of the plenum 32, according, in
part, to the space available within different areas of the plenum
32. For example, as shown in FIGS. 2 and 3, the bottom 62 of the
plenum 32 may be closer to the diffuser output 44. Therefore, the
sloping surfaces 50 may be sloped more rapidly toward the bottom of
the plenum 32. Furthermore, in some embodiments, as will be more
clearly shown in FIG. 4, the sloping surfaces 50 may be formed by
two cones 78 positioned across from each other on opposite sides of
the plenum 32.
[0028] After the combustion gases enter the plenum 32, the plenum
32 then gradually guides the combustion gases toward the same
direction along the z-axis 35, where they eventually exit the
plenum 32 at the plenum output plane 80. The plenum 32 may also
include a tapered output transition 82 that gradually expands the
width of the plenum 32 to match the width of the next downstream
exhaust component. Also included in the plenum 32 is a flow
splitter 84 that guides the combustion gases from the diffuser
output 44 to the plenum output 80. As discussed below, the flow
splitter 84 is configured to reduce recirculation zones, reduce the
concentration of flow along the walls, and increase the uniformity
of the flow in the forward direction through the 32. As shown in
FIG. 3, the flow splitter 84 spans the width of the plenum 32,
extending completely across the plenum 32 along the x-axis 31.
Accordingly, the flow splitter 84 is tapered to match the contour
of the sloping surfaces 50 and the output transition 82.
[0029] The flow splitter 84 provides a number of advantages. For
example, the flow splitter 84 may inhibit swirling flow and
recirculation zones inside the plenum 32. For another example, the
flow splitter 84 may also guide a portion of the combustion gases
away from the top 60 of the plenum 32 and toward the middle of the
plenum 32, thereby increasing the uniformity of flow out of the
plenum 32 and reducing high pressure regions along the plenum wall.
In other words, the flow splitter 84 reduces the concentration or
attachment of the flow along the walls of the plenum 32 by
redirecting at least some portion of the flow toward a more central
region within the plenum 32. The flow splitter 84 also aids in
directing the flow in a forward or downstream direction (i.e.,
mostly forward velocity vectors) along the z-axis 35 through the
plenum 32, rather than allowing the flow to vary in direction
throughout the plenum 32. Each of theses advantages may serve to
reduce the backpressure on the turbine engine 12. In certain
embodiments, the sloping surfaces 50 and the flow splitter 84 may
be configured to provide a minimum variation in mass distribution
across the plenum 32 (e.g., across the cross-section transverse to
the flow direction along the z-axis 35) relative to an average
value across the plenum 32. Again, the sloping surfaces 50 and the
flow splitter 84 may be configured to improve the aerodynamics by
reducing flow resistance, reducing turbulence, reducing
recirculation zones, improving the distribution or uniformity of
flow, and reducing back pressure. As will be described below, the
plenum 32 may, in some embodiments, include several flow splitters
84. Other details of the tapered output transition 82 and the flow
splitter(s) 84 may be better described with reference to FIGS. 4
and 5.
[0030] FIG. 4 is a cut-away top view of an embodiment of the plenum
32 as shown in FIG. 3. Additionally, a portion of the flow splitter
84 is cut-away to show the sloping surfaces 50 on both sides of the
plenum 32. As can be more clearly seen in FIG. 4, the sloping
surfaces 50 may be formed by two cones 78 positioned across from
each other on opposite sides of the plenum 32 sidewalls with an
axial offset along the x-axis 31 that forms the initial width 48 of
the plenum 32. As illustrated, the cones 78 diverge away from one
another with radial distance from the x-axis 31. The axial offset
between the sloping surfaces expands at greater radial distances
from the x-axis 31 out to the full width 52 of the plenum 32, as
describe above in relation to FIG. 2. As stated above in relation
to FIG. 2, the slope angle 56 of the sloping surfaces 50 formed by
the cones 78 may range between approximately 0 to 60 degrees or 5
to 45 degrees, or any specific angle in between. In one embodiment,
the slope angle 56 may range between approximately 10 to 30
degrees. Accordingly, the rate at which the sloping surfaces 50
diverge away from one another may be approximately 35 to 115
percent of a change in axial offset versus a change in radial
distance. It should also be noted that, as viewed from the top as
in FIG. 4, the geometry of the cones 78 may be substantially the
same on both sides of the x-axis 32, i.e. the cones 78 may be
symmetrical about the x-y plane. Therefore, the slope on opposite
sides of the x-y plane may be substantially the same. It can also
be more clearly seen in FIG. 4 that the flow splitter 84 extends
across the full width of the plenum 32, adhering to the contours of
the cones 78 and the tapered output transition 84. Furthermore, it
can also be seen that the diffuser output 44 may be centered within
the plenum 32 in the x-axis 31 direction and that the height 79 of
both cones 78 may be approximately the same.
[0031] FIG. 5 is a cut-away side view of an embodiment of the
plenum 32 shown in FIGS. 1-4. As is shown in FIG. 5, the back side
118 of the plenum 32 may be shaped to more closely conform to the
circular contour of the diffuser output 44. This may serve to
inhibit low pressure pockets that may otherwise form at corners of
the plenum 32, thereby reducing turbulence and backpressure. As
shown in FIG. 5, the backside 118 of the plenum 32 may be defined
by segments, e.g. formed by flat plates 120, which are configured
to roughly approximate a rounded surface. Segmenting the backside
118 of the plenum 32 with flat plates 120 may reduce the expense of
fabricating the plenum 32 with a curved surface. In other
embodiments, the back side 118 of the plenum 32 may be square,
which may make the flow splitter 84 easier and less expensive to
fabricate. However, certain embodiments of the plenum 32 may have a
curved backside 118, e.g., semi-circular shape, which may further
reduce the turbulence and backpressure.
[0032] Additionally, as shown in FIG. 5, the diffuser output 44 may
be positioned in the turbine exhaust plenum at an off-center
position relative to the x-axis 31. In other words, the diffuser
output 44 may be closer to the bottom 62 of the plenum 32 than the
top 60 of the plenum 32. Furthermore, the flow splitter 84 may be
disposed toward the top 60 of the plenum 32 in relation to the
diffuser output 44. It can also be seen in FIG. 5 that the diffuser
output 44 and the cones 78 may not be concentric. For example, a
center 102 of the cone 78 may be shifted along the y-axis 33
approximately 6 to 12 inches above a center 104 of the diffuser
output 44. In certain embodiments, the offset between centers 102
and 104 may be at least greater than approximately 2.5 5, 7.5, 10,
15, 20, or 25 percent of the diameter of the diffuser output 44. In
some embodiments, the offset between centers 102 and 104 may depend
on the amount of offset of the diffuser output 44 in the plenum
32.
[0033] Also shown in FIG. 5, is an exemplary flow splitter 84,
which spans from the diffuser output 44 to the plenum output 80.
For purposes of the specifying particular angles about the diffuser
output 44, the z-axis 35 is herein defined as pointing toward 0
degrees, while the y-axis 33 is herein defined as pointing toward
90 degrees. Additionally, an upstream or "leading" edge 106 of the
flow splitter 84 will be considered the edge closest to the
diffuser output 44, and a downstream or "trailing" edge 108 of the
flow splitter 84 will be considered to be the edge closer to the
plenum output plane 80.
[0034] Accordingly, as shown in FIG. 5, the leading edge 106 of the
flow splitter 84 may be positioned at approximately 90 degrees.
Furthermore, the leading edge 106 of the flow splitter 84 may begin
at the narrowest point between the two sloped surfaces 50, e.g. at
the place where the cones 78 meet the diffuser output 44. The flow
splitter 84 may then extend radially outward for a short distance
110 of approximately 6 to 12 inches before bending toward the
plenum output 80. In some embodiments, the flow splitter bends at
least approximately 90 degrees from the radial, i.e., y-axis 33,
direction to the downstream, i.e., z-axis 35, direction. In some
embodiments, the flow splitter 84 may curve gradually from the
diffuser output 44 to the plenum output 80 to further inhibit
turbulent flow. However, in some embodiments, the flow splitter 84
may be segmented, as shown in FIG. 5, which may make the flow
splitter 84 easier and less expensive to fabricate while still
maintaining significantly low turbulence. In other words, the flow
splitter 84 may include a plurality of flat plates in series to
define the desired turn from the leading edge 106 to the trailing
edge 108. Furthermore, in some embodiments, the flow splitter 84
may complete or substantially complete the turn (e.g.,
approximately 90 degrees) within the confines of the cones 78. In
other embodiments, the flow splitter 84 may complete a portion
(e.g., 50 percent) of the turn within the confines of the cones 78,
while finishing the turn beyond the cones 78.
[0035] The flow splitter 84 extends generally downstream in the
z-axis 35 direction to an axial offset position away from the
radial diffuser. The total length of the flow splitter 84 may
generally be greater than the radius 122 of the diffuser output 44.
Furthermore, in certain embodiments, a percentage of the radial
length (e.g., distance 110) versus the axial length (e.g., beyond
110) may be at least less than approximately 5, 10, 15, 20, 25, 30,
or 35 percent. In some embodiments, the trailing edge 108 of the
flow splitter 84 may be substantially flush with the plenum output
80 and may bisect the plenum output 80 into a top section 112 and a
bottom section 114. In some embodiments, the height 116 of the
bottom section 114 may be approximately 50 to 60 percent of the
overall height 58 of the plenum 32. Furthermore, the relative
height of the top section 112 and the bottom section 114 may be
chosen, in some embodiments, to provide substantially equal
air-flow velocity at the plenum output 80 in both the top section
112 and the bottom section 114. The functioning of the flow guide
84 may be better understood with reference to FIG. 6
[0036] FIG. 6 is a cut-away side view of the plenum 32 of FIG. 5,
illustrating an example of the air flow in an embodiment of the
plenum 32. When the exhaust gases exit from the diffuser output 44,
the direction of flow may be substantially radial, i.e. away from
the x-axis 31, as illustrated by the solid lines 128. Shortly after
exiting the diffuser output 44, some of the combustion gases may
begin to take on a circumferential flow, depending on which side of
the diffuser output 44 that the combustion gases exit from. The
combustion gases exiting toward the plenum output 80 may tend to
travel substantially linearly from the diffuser output 44 directly
to the plenum output 80. Meanwhile, gases exiting toward the
backside 118 of the plenum 32, opposite the plenum output 80, will
travel circumferentially around the diffuser output 44 toward the
plenum output 80.
[0037] Without the flow splitter 84, more of the combustion gases
exiting the diffuser output 44 may tend to be directed toward the
top 60 of the plenum 32, as indicated by the dotted line 130,
resulting in increased air pressure at the top 60 of the plenum 32,
reduced air pressure toward the center of the plenum 32, and a more
turbulent air flow that may extend through other downstream exhaust
components. With the flow splitter 84, more of the combustion gases
are directed more immediately toward the center of the plenum 32,
resulting in more uniform flow characteristics from the top 60 to
the bottom 62 of the plenum 32 and reduced turbulence. Furthermore,
the increased flow uniformity may also extend to other downstream
exhaust components such as the silencers 34 (FIG. 1). The net
result may be a drop in backpressure, which increases the
efficiency of the turbine engine 12.
[0038] FIGS. 7 and 8 are cut-away side views of additional
embodiments of the plenum 32 which may provide even further reduced
backpressure. Turning first to FIG. 7, a plenum 32 with two flow
splitters is shown. As with the first flow splitter 84, the second
flow splitter 130 also serves to guide the combustion gases toward
the plenum output 80 and reduce turbulence. The second flow
splitter 130, however, provides additional flow guidance for
combustion gases exiting more toward the back side of the plenum
32. Accordingly, a leading edge 132 of the second flow splitter 130
may begin at approximately 90 to 180 degrees, 110 to 160 degrees,
or approximately 135 to 150 degrees, or any specific angle in
between. In the illustrated embodiment, the leading edge 132 is
located at approximately 135 degrees. Additionally, as with the
first flow splitter 84, the leading edge 132 of the second flow
splitter 130 may be positioned at the narrowest point between the
two sloped surfaces 50 (e.g., cones 78). The second flow splitter
130 may then extend radially outward for a short distance 134 of
approximately 6 to 12 inches before bending toward the plenum
output 80. In some embodiments, the second flow splitter 130 may
curve gradually from the diffuser output 44 to the plenum output 80
as shown in FIG. 7. In this way turbulent flow toward the backside
118 of the plenum 32 may be further inhibited.
[0039] The trailing edge 136 of the second flow splitter 130 may be
located at approximately the 60 to 90 degree position. In other
embodiments, which will be shown in FIG. 8, the trailing edge 136
of the second flow splitter 130 may be flush with the plenum output
80 and may section the plenum output 80 into three sections.
However, the flow splitter 130 may have any suitable
circumferential length or angular span from the leading edge 132 to
the trailing edge 136. For example, the flow splitter 130 may have
a circumferential length of approximately 90, 100, 110, 120, 130,
140, 150, 160, 170, or 180 degrees. A gap 138 between the first
flow splitter 84 and the second flow splitter 130 may be maintained
at approximately 0.5 to 1.0 times the initial width 48 of the
plenum (see FIG. 2). In some embodiments, the gap 138 may be
approximately 12 to 28 inches. Furthermore, the gap 138 may be
selected to provide equal air flow velocity on both sides of the
second flow splitter 130 at the trailing edge 136 of the second
flow splitter 130.
[0040] Turning now to FIG. 8, a symmetrical plenum 32 is shown. As
shown in FIG. 8, the plenum 32 is symmetrical about the Z-axis 35.
For example, the top side 60 and the bottom side 62 are equally
spaced (and thus symmetrical) about the cones 78 and the diffuser
output 44. Likewise, the flow splitters 84 and 130 are equally
spaced (and thus symmetrical) between the top and bottom sides 60
and 62 and the diffuser output 44. Furthermore, as discussed above,
the second flow splitters 130 may extend to the plenum output plane
80 while maintaining the gap 138 as described above. As such, the
plenum output 80 may be divided into five sections, two top
sections 140, a middle section 142, and two bottom sections 144. In
some embodiments, the flow splitters 84 and 130 may be positioned
such that the relative height of each of the five sections 140,
142, and 144 may be approximately proportional to the relative air
flow through each section, thus providing approximately equal air
flow velocity through each of the sections 140, 142, and 144 at the
plenum output plane 80. In certain embodiments, the height 146 of
the two top sections 140 may be approximately 12.5 percent of the
overall height 58 of the plenum 32 and may each provide
approximately 12.5 percent of the air flow exiting the plenum 32.
Additionally, the height 148 of the two bottom sections 144 may be
approximately 12.5 percent of the overall height 58 of the plenum
32 and may each also provide approximately 12.5 percent of the air
flow exiting the plenum 32. Accordingly, the height 150 of the
middle section 142 may be approximately half of the overall height
58 of the plenum 32 and may provide approximately half of the air
flow exiting the plenum 32.
[0041] As is also shown in FIG. 8, the backside 118 of the plenum
32 may be rounded to more closely conform to the circular contour
of the diffuser output 44. This may serve to inhibit low pressure
pockets that may otherwise form at corners of the plenum 32,
thereby reducing turbulence and backpressure. The result is a
substantially more uniform, laminar flow with less turbulence and
backpressure.
[0042] The exhaust system disclosed herein use a variety of
techniques that reduce backpressure and thereby enable increased
efficiency for gas turbine engines. For example, embodiments
disclosed herein provide gradual expansion of combustion gases
within the plenum 32 along a gradually sloping surface. For another
example, embodiments disclosed herein provide flow splitters 84 and
130 that guide the combustion gases away from the walls of the
plenum 32 and toward the center of the plenum 32, thus making the
flow within the plenum 32 more uniform and reducing air friction
between the combustion gases and the walls of the plenum 32. In
certain embodiments, the plenum 32 may include any number and
configuration of flow splitters, e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9,
10, or more flow splitters on one or both sides 60 and 62 of the
diffuser output 44. For example, the flow splitters may be disposed
at increments of 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, or
90 degrees about the circumference of the diffuser output 44. As a
result, depending on the location of the leading edge along the
circumference of the diffuser output 44, the flow splitter may have
a greater or lesser turn angle. Furthermore, the improved flow
characteristics may also extend to exhaust components further
downstream. Furthermore, the flow characteristics may be further
improved by making the exhaust plenum symmetrical and/or making the
back side of the plenum 32 rounded. Employing one or more of the
disclosed improvements in various combinations may result in less
turbulent air flow, increased flow uniformity, and reduced
backpressure in the plenum and other parts of the exhaust system.
Furthermore, the exhaust system described herein may be more
compact and use less material compared to typical exhaust plenums,
which may save both space and money.
[0043] This written description uses examples to disclose the
invention, including the best mode, and also to enable any person
skilled in the art to practice the invention, including making and
using any devices or systems and performing any incorporated
methods. The patentable scope of the invention is defined by the
claims, and may include other examples that occur to those skilled
in the art. Such other examples are intended to be within the scope
of the claims if they have structural elements that do not differ
from the literal language of the claims, or if they include
equivalent structural elements with insubstantial differences from
the literal languages of the claims.
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